Production of leukotrienes in a model of focal cerebral ischaemia in the rat

Abstract

1. The aim of this work was to evaluate the role of leukotrienes in brain damage in vivo in a model of focal cerebral ischaemia in the rat, obtained by permanent occlusion of middle cerebral artery. 2. A significant (P < 0.01) elevation of LTC(4), LTD(4) and LTE(4) (cysteinyl-leukotrienes) levels occurred 4 h after ischaemia induction in the ipsilateral cortices of ischaemic compared to sham-operated animals (3998 +/- 475 and 897 +/- 170 fmol g(-1) tissue, respectively, P < 0.01). 3. The NMDA receptor antagonist MK-801 and the adenosine A(2A) receptor antagonist SCH 58261 were administered in vivo at doses known to reduce infarct size and compared with the leukotriene biosynthesis inhibitor MK-886. 4. MK-886 (0.3 and 2 mg kg(-1) i.v.) and MK-801 (3 mg kg(-1) i.p.) decreased cysteinyl-leukotriene levels (-78%, P < 0.05; -100%, P < 0.01; -92%, P < 0.01, respectively) 4 h after permanent occlusion of the middle cerebral artery, whereas SCH 58261 (0.01 mg kg(-1) i.v.) had no significant effects. 5. MK-886 (2 mg kg(-1) i.v.) was also able to significantly reduce the cortical infarct size by 30% (P < 0.05). 6. We conclude that cysteinyl-leukotriene formation is associated with NMDA receptor activation, and that it represents a neurotoxic event, the inhibition of which is able to reduce brain infarct area in a focal ischaemic event.

Figure 1

Time course of the variation of cysteinyl-LT levels in the contralateral cortices from sham-operated and ischaemic animals and in the ipsilateral cortices from sham-operated animals. Data are means±s.e.mean, n=3–5. (^*P<0.05 vs contralateral cortices). Statistical analysis was performed by two-way ANOVA followed by Bonferroni's test.

Figure 2

Time course of the variation of cysteinyl-LT levels in the ipsilateral cortices from ischaemic animals compared with reference values (ipsilateral sham-operated cortices). Data are means±s.e.mean, n=4–9. (^**P<0.01 vs sham-operated cortices). Statistical analysis was performed by two-way ANOVA followed by Bonferroni's test.

Figure 3

Variation of cysteinyl-LT levels in ischaemic cortices induced by in vivo administration, of MK-801 (3 mg kg⁻¹ i.p.), SCH 58261 (0.01 mg kg⁻¹ i.v.) and MK-886 (0.3 and 2 mg kg⁻¹ i.v.). Cysteinyl-LT levels were assayed 4 h after pMCAo. Inhibition was evaluated by taking cysteinyl-LT formation in ipsi-lateral sham-operated cortices as basal value. Data are means±s.e.mean, n=4–10. (^*P<0.05 and ^**P<0.01 vs ischaemic cortices). Statistical analysis was performed out by one-way ANOVA followed by Bonferroni's test.

Figure 4

Total, cortical and striatal infarct volume 24 h after pMCAo in rats treated with either MK-886 (2 mg kg⁻¹ i.v.) or vehicle after pMCAo. Data are means±s.e.mean, n=10–13. (^*P<0.05 vs vehicle; statistical analysis was performed by two-way ANOVA followed by Dunnett's test for multiple comparison).